I have exactly the same problem. Does anybody have a solution?
I would really like to use leJOS. It works fine as long as I only use the library classes.jar. Now I need to send commands from a PC to the RCX, so I have to use the RCXPort.
I think it is a classpath-problem, because in my error message the classpath is written down, but the rcxcomm.jar is not referenced although it is linked in eclipse... It seems to me, that the Eclipse-Plugin doesn't use the classpath provided by eclipse.
Class josx.rcxcomm.RCXPort (file josx/rcxcomm/RCXPort.class) not found in CLASSPATH C:\...\eclipse\plugins\org.lejos_1.2.0\lib\classes.jar;C:\...\eclipse_workspace\Test\bin
Thanks for any hints...